How To Choose Turquoises Jewelries
How To Choose Turquoises Jewelries
Turquoise, the "Skystone" blessed by Mother Earth decorates our life for centuries. To determine the quality of a natural turquoise, the basic mineralogy knowledge may be needed. Also, the hardness, matrix, color and rarity are all the factors determine the turquoise quality. Not to be surprised, the price tag can vary as huge as factor of 10s in jewelry market depend on its quality and rarity. In addition, the uniqueness in design is also high appreciated.
In terms of turquoise quality, one article that covers this topic comprehensively is found from www.americana.net by Lee Anderson. We are referring the whole article from Mr. Anderson.
By Lee Anderson
Source: Click Here
We could write pages on this and still not cover the subject. In the earliest of times — up to the late 1800s — certainly, the pure blue without matrix was considered the best. It was time-tested; if the color did not change it was “old rock”…in other words, a gem! If the color did change, it was “new rock,” inferior and impermanent. While the pure blue stone could be gem quality, the matrixed stone was not considered a gem stone. This all changed in the late 19th century, when the American Indian developed a preference for the matrixed stone, causing an entire new grading criteria to evolve.
Today, the preferred turquoise in the Middle East is still the pure blue. As such, great quantities of rather inferior stabilized “chalk” turquoise have been shipped there for sale to local jewelers and merchants. People have brought me pieces they bought in bazaars and markets as “old Persian or Arab” jewelry that was actually made from Kingman stabilized turquoise. Beware!
Criteria for Grading Turquoise in the U.S.
Hardness / Density. This is a critical factor in determining the grade of a turquoise specimen. An inferior, chalk-like turquoise will feel light; it will be porous and stick to your tongue. The harder, denser pieces will have a “good” substantive feel to them. They will not draw the same quantity of moisture from your tongue as lower grades, but you will feel some adhesion to your tongue. As density increases, so too does hardness. Just as turquoise varies from a little over 2 to nearly 6 on the Mohs scale, its specific gravity also varies but typically is 2.8, like quartz.
Luster. This should come from within the stone — not just from a surface polish.
Color. No area is less codified than this. The ancients preferred blue because a gem-grade blue stone would not change color (King Tut’s treasures include a substantial amount of blue turquoise — it appears today unchanged). Because the softer blue stones would eventually start turning greenish, it was assumed that green was not as good. Time has proven this wrong. Some green-hued turquoise such as Skyhorse, China Mountain (both are names given to turquoise from China), Cerillos, Blue Gem, and Fox, to name a few, are ranked in the top three grades, like blue stones from the Lander, Lone Mountain, Red Mountain, Morenci, and Bisbee mines. To make matters even more difficult, some mining areas — such as Skyhorse, China Mountain, Blue Gem, and Royston — produce both colors.
Matrix. This is the host rock in which the turquoise forms and bonds. When cut, the host rock and the turquoise are one piece. The pattern of this matrix must be pleasing. This is subjective at best, but with experience, you learn what most people consider most desirable. Again, as in color, the opinions on which matrix is “best” varies dramatically. There are hard-core supporters of the fine, dark, spider web found in the Lander, Number Eight, Lone Mountain, Red Mountain, Skyhorse, and China Mountain mines. The heavy brown-black matrix of Bisbee and Tyrone has followers who believe it is the world’s best. A hard, lustrous cabochon from Morenci typifies another beautiful and highly regarded matrix. It is freeform, with a blending of webbing and deep pattern matrix combined with visible pyrite inclusions.
In a given cabochon of turquoise, any of the above could qualify as “best.” depending on the personal preferences of the one judging. However, when mounted in jewelry, you must consider the balance of the turquoise in the setting by itself or in combination with other stones.
Rarity. People covet that which is rare, and value escalates accordingly. A stone from a mine that produced a highly collectible stone that has subsequently closed appeals more to a collector then a stone from an active mine. Again, the other factors discussed above must also apply; rarity is simply the price discriminator. For example, a beautiful five-carat cabochon of deep-blue turquoise with a tiny black spider web matrix from the Lander Mine in Nevada (closed many years ago) has a retail value of $2,000 to $2500. A similar cabochon from the Lone Mountain Mine, also closed, would be $750 to $800. It is every bit as good — and, in the case of the matrix, better — but the mine produced for a longer time. A similar cabochon from the Skyhorse Mine from Tibet and China would be nearer $75 because it is still active and produces large quantities of turquoise.
Another good article by Mr. Lee Anderson:
How the Quality of Turquoise Affects Its Use in Jewelry